It is known to apply labels to containers or bottles to provide information such as the supplier or the contents of the container. Such containers and bottles are available in a wide variety of shapes and sizes for holding many different types of materials such as detergents, chemicals, personal care products, motor oil, beverages, etc.
Polymeric film materials and film facestocks have been used as labels in various fields. Polymeric labels are increasingly desired for many applications, particularly transparent polymeric labels since they provide a no-label look to decorated glass and plastic containers. Paper labels block the visibility of the container and/or the contents in the container. Clear polymeric labels enhance the visual aesthetics of the container, and therefore the product. The popularity of polymeric labels is increasing much faster than that of paper labels in the package decoration market as consumer product companies are continuously trying to upgrade the appearance of their products. Polymeric film labels also have superior mechanical properties as compared to paper labels, such as greater tensile strength and abrasion resistance.
Traditional polymeric pressure sensitive (PSA) labels often exhibit difficulty adhering smoothly to containers having curved surfaces and/or complex shapes without wrinkling, darting or lifting on the curved surfaces. As a result, heat shrink sleeve labels have typically been used on these types of containers having compound curved surfaces. Direct screen printing is another method for applying indicia or other markings to curved surfaces. Labeling operations for heat shrink sleeve type labels are carried out using processes and methods that form a tube or sleeve of the heat shrink film that is placed over the container and heated in order to shrink the film to conform to the size and shape of the container. Alternatively, the containers are completely wrapped with a shrink label using a process in which the shrink film is applied to the container directly from a continuous roll of film material and then heat is applied to conform the wrapped label to the container. Regardless, label defects frequently occur during labeling operations of simple or compound shaped bottles during label application or in post label application processes. These misapplied labels result in high scrap or extra processing steps that can be costly.
Other processes for applying pressure sensitive shrink labels are known. In certain applications, a label is applied onto a container, heated, and any resulting defects then wiped to minimize such defects. A potential problem exists with a separate heat and wipe process with pressure sensitive shrink labels where edge defects are initially formed and then removed. Although the formation of the edge defects typically occurs in the same general region of the bottle, the defects are not in the exact same spot, nor of the same size or occur in the same number. These defects, collectively referred to herein as “darts” can in certain instances, be shrunk with heat. As these defects shrink, the area of the label comprising the dart is reduced along with the ink and print on top of the label dart. The shrinkage of the dart will shrink the print as well cause distortion of the print. Depending on the size of the dart and print fidelity, the distortion might be noticed and can in certain cases, be significant. This distortion may limit the type or quality of print in the shrink region of the label. Therefore, avoiding the formation of darts entirely would be of great benefit.
Accordingly, a need exists for a process and related system in which a shrink label could be applied to a curved surface and particularly a compound curved surface without the occurrence of darts or other defects.